Mist injection method and system

ABSTRACT

The disclosure teaches a method for more efficiently practicing in-situ combustion techniques by generating a gaswater mist or foam adjacent the combustion formation within the injection well. The mist or foam is forced out of the well into the formation to transport heat away from the burned region of the formation toward the periphery of the combustion region to conserve fuel. Also taught are a method and system for fluid treating a formation while maintaining enhanced conformance of the fluid injection profile by generating a mist or foam downhole adjacent the formation and then forcing the mist or foam out into the formation.

PME51 v -wu memes fateill [191 Bradley et al.

[451 Sept. 16, 1915 1 MES? INJEQ'IIGN METHOD AND SYSTEM [73} Assignee:

[22} Filed:

Sun {121 Company (Dela 131111113, Tex.

[21} Appl. No; 385,373

1 int BQSB /1111; B213 43/25; E21B 43/24 1531 Field asemhum 166/260, 305 12,2 1: 2391124, 125. 200, 289, 318, 589, 590.3, 601

Rdcrenccs Cited UNlTliD STATES PAT 3,687,202 8/1972 Young et al. 165/365 R 3,722,594 3/1973 Smith et a] 1661305 R FOREIGN PATENTS 0R APPLICATIONS 1,197,685 6/1959 France 239/5903 870,995 6/1961 United Kingdcm..... 239/124 1,227,333 4/1971 United Kingdom.... 39/318 Primary Examiner-Robert S. Ward, Jr. Azzomey, Agent, or Firm-George L. Church; Donald R. Johnson; John E. Holder .[57] ABSTRACT The disclosure teaches a method for more efficiently practicing in-situ combustion techniques by generating a gaswater mist or foam adjacent the combustion formation within the injection-well. The mist of foam is forced out of the well into the formation to transport heat away from the burned region of the formation toward the periphery of the combustion region to conserve fuel. Also taught are a method and system for fluid treating a formation while maintaining enhanced conformance of the fluid injection profile by generating a mist or foam downhole adjacent the formation and then forcing the mist or foam out into the formation.

, 5 Claims, 3 Drawing Figures I MIST [NIEC'HON METHGD AND SYSTEM BACKGROUND OF THE ENVEN'HON The invention relates to fluid treatment of-a formation penetrated by a weilbore and, more particularly, to a method and system for fluid treating a formation while producing an enhanced conformance of the fluid u-eatrnent injection profile the formation. The invention is mpeciady useful in increasing the efficiency of an in-sitn combustion, pet oleum recovery process.

in the petroleum production industry a number of techniques have been developed for fluid treating subterranean formations penetrated by a wellbore. In order to produce an even distribution of fluid within the formation it would be desirable to suspend the treatment fluid as a mist within a carrier fluid. ln certain prior art systems, a mist comprising a treatment fluid, such as acid, and a gas have been injected into the wellbore face at the surface of the well. Unfortunately, on the way down the well to the formation, the mist generally condenses onto the sides of the tubing while the gas flows down the center producing a two phase flow and defeating the original purpose of misting. In an attempt to maintain even distribution of treatment fluid others have generated a foam at the well surface and then attempted to force the foam down the tubing and out into the formation. This is a very inefficient technique and usually degrades the foam pr or to reaching the formation.

Fluid treatment systems such as those disclosed in US. Pat. No. 3,215,197 to Kiel and U.S. Pat. No. 3,599,717 to McMillen have-sought to avoid surface injection problems by transporting two different fluids downhole in separate conduits. Kiel injects the fluids through separate perforations to nib; within the formation while McMillen allows the fluids to randomly mix in the casing or the first few feet of the formation. Both of these techniques lead to uneven distribution of fluids within the formation and, in the event one of the fluids is a gas and the othera liquid, theywill probably remain in two phase flow producing a further degradation of conformance.

Other prior art treatment teclmiques, such as those shown in US. Pat. No. 3,460,623 to beach and US. Pat. No. 3,491 ,832 to Raza, generate foam within a formation by first introducing a liquid foaming agent into the formation and then injecting a gas to produce foam within the interstices of the formation particles. These methods rely upon the homogeneity of the formation to produce a high quality foam which-unfortunately, is

often of degraded quality due to a dirty formation.

It is therefore an object of the present invention to provide anew and improved, method and system for fluid treatment ofsubterranean formations by g'enerat ing a mist or a foam downhole within the well and'adjacent the formation and then forcing the mist or foam out into the formation. The present invention produces an enhanced conformance ofthe treatment fluid injecoil around the injection well by some convenient;

method such as an electrical heater, gas burner or chemical reaction; and (3) continuing the injection of air to propagate a combustion region through the oil reservoir from the injection well to the producing well where the combustion liberated oil is recovered. After an extended period of operation a forward burn leaves behind it an enormous guantity of heat trapped in the rock in the burned region of the formation. A substantial quantity of formation contained hydrocarbons are sometimes consumed in the combustion region. If, however, some of the heat trapped in the burned reg'on of the formation could be transported toward the periphery of the combustion region it would result in more efficient hydrocarbon displacement and a lower consumption of recoverable hydrocarbons.

lt is therefore another object of the present invention to provide an improved in-situ combustion method by injecting a mist or foam of heat absorbing fluids into the combustion formation with a relatively uniform injection profile. The mist penetrates the formation to transport heat away from the burned region of the formation toward the periphery of the combustion region.

SUMMARY OF THE INVENTIQN With these and other objects in view, the present invention contemplates an improved method and injector for fluid treating a formation penetrated by a wellbore to enhance conformance of the treatment fluid injection profile within the formation. A mist, comprising a suspension of treatment fluid in one phase within a carrier fluid in a different phase, is generated by the injector within the wellbore adjacent the formation to be treated. The mist is forced out of the wellbore into the formation to produce a relatively uniform injection profile of treatment fluid within the formation.

The injector for generating the mist includes a section of tubing terminated at the lower end by a collar. The injector has an inlet section having an aperture therein for admitting fluids; an intermediate section attached to the lower end of the inlet section and sealed to the interior of the collar; and an outlet section including a spray orifice for production of a mist from fluid flowing through the injector and a diverging nozzle to direct the trajectory of the mist.

BRIEF DESCRIPTION OF THE DRAWINGS bodiment of an injector constructed in accordance with the invention;

tion profile over known prior art systems and tech- H6. 2 a longitudinal cross-section view of an alternate embodiment of an injector constructed in moor dance with the invention; and I Fit]. 3 is a transverse cross-section view taken about the lines 3-3 of FIG. 2.

DETAILED DESCRIPTION Referring first to FIG. 1, there is shown a mist and foam injector tool :0, constructed in accordance with the invention and located within a well casing 11. The casing 11 penetrates a hydrocar oon bearing formation 12 to be treated and includes a plurality of mrforations 13 which provide fluid communication between the interior of the casing and the formation. The injector is attached to the lower end of the section of tubing 14 by means of a collar 15, such as a pump seating nipple, which is internally threaded at each end. The tubing 14 may be centered within the casing 11 by means of a packer or centralizer (not shown) if necessary to achieve stability. The upper end 16 of the collar threadedly engages the lower end of the tubing 14 while the intermediate portion 12 is formed by a cylindrical surface of reduced internal diameter. The upper edge of the intermediate portion 17 includes an annular abutment 18.

The injector 10 comprises an inlet section 21, an intermediate section 22 and an outlet section 23. The inlet section 21 is generally dome-shaped with a plurality of apertures 24 therein. An internally threaded socket 25 is formed in the center of the interior of the inlet section 21 while an externally threaded projection 26 is positioned in the top center of the exterior. A fishing neck 27 is threaded to the projection 26 to allow convenient removal of the tool from the opening of the well tubing 14. The inlet section 21 threadedly engages the top of the intermediate section 22 which includes an outwardly flaring annular ridge 28, cylindrical side walls having an annular groove 29 formed therein and an externally threaded lower end. When positioned as shown in FIG. 1, the ridge 28 is fitted against the annular abutment l8 and the intermediate section 22 is sealed to the 15 by a sealing member 31, such as an O- ring positioned in the groove 29.

The threaded lower end of the intermediate section 22 is attached to the upper end of the outlet section 23 to form the three sections 21-23 into a substantially smooth, continuous internal surface. The interior surface of the outlet section 23 converges at the lower end to a high velocity spray orifice 32 and then diverges to a symmetrical nozzle portion 33.

In operation, a two phase mixture of two or more fluids is delivered from the surface by external sources such as a pump, and/or a compressor (not shown) and is forced down through the tubing 14 in thedirection of arrow 41. A typical tubing pressure which has been shown to operate successfully to generate a mist with air and water is about 860 psi. when the casing pressure is about 800 psi. The fluids pass through the apertures 24 and into the injector body where they are mixed further by turbulent flow. in certain instances it may be desirable to include flow straightening vanes (not shown) within the body of the outlet section 23 to reduce some of the turbulence before passing through the spray orifice 32. Finally the fluids pass through the high velocity spray orifice 32 and out of the injector through the diverging noale. 33 in a fine mist 42. The

injector' 10 is preferably positioned longitudinally within the casing 11 so that the mist 42 strikes and extends actively along the perforated casing wall in the region adjacent the formation to be treated 12.

Many difi'erent fluids could be used to generate a mist in the injector of the present invention, for exampie, 3 gas and a liquid such as air and water, CO and water, air and acid, or nitrogen and acid; a gas and a solid, such as air and talc; or a liquid and a solid suspension. A foam, rather than a mist, is produced by the injector 10 when a gas and a foaming agent liquid are forced through the nozzle 33. Foaming agent liquids are well known in the art and a number of typical foamwell.

ing agents are discussed in US. Pat. No. 3,330,346 to Jacobs et al.

The production of amist downhole at a location adjacent the formation to be treated and then the injecu'on of that mist into the formation due to casing pressure produces an improvement of fluid injection profiles over prior art injection methods. In particular instances, the production and injection of a foam may produce even better conformance than with a mist.

When the system of FEG. I is used to generate a mist, such as from air and water, the density of the mist may be controlled by varying the relative amounts of each fluid. If, however, water begins to accumulate in the bottom of the. well hole the embodiment of the inventier: shown in FIG. Zmay he used effectively. The apparatus of FIG. 2 isfl'enfical to thatof FIG. 1 except for the addition of an aspirator sump tube 51 fitted into the threaded socket 25. A three armed support web 34 (best shown in FIG. 3) having a central opening 35 is positioned in thelower end of the nonle. The tube 51 extends along the axis of the injector 10, through the aperture 35 and is transversely braced by the web 34. The interior of the tube 51 is open via an aperture 50 to the reduced pressure within the high velocity spray orifice 32. The tube 51 is open at its lower end and terminated only by a sump screen 52, located in the rat hole 53. As water mcumulates in the bottom of the well, it is aspirated up and remisted out the nozzle 33.

The present injector and formation treatment method can be used in the improved in-situ combustion recovery process. The basic technique, arch as the forward burn are well known in the art, for example, see US. Pat. No. 3,452,816 to Hardy et aL, which is assigned to the assigneeof the present invention. In general, forward bum involves at least two wells which penetrate the wmbustion formation, an injection well and a production well. Air-is flowed down the injection well and through the ibrmation toward the production well. Hydrocarbons in the formation near the injection well are externally ignited and the injection of air is continued to propagate a combustion region through the oil reservoir toward the production well. As the combustion continua a number of identifiable zones are produced within the reservoir. First, in the vicinity of the injection well there "a aburnedmne, the temperature of which may rangefrom a few hundred degrees F up to 1,6001. Next, in the direction of flow, is a combustion zone whkh may range in temperature from 550F, to 1,200? depending upon the type and quantity of hydrocarbon material available for fuel within the formation. Finally, there is a condensation zone which provides fuel for the encroaching combustion zone andmoves the oil bank toward the production Became of the high temperatfires'and the insulating characteristics of'the formation, atreinendous amount of heat may be stored within the burned region. if,-

' rather than being lost to the rock, th s heat is recovered absorbing fluid and injecting the mist into the formation 12 with a relatively uniform injection profile. heat is transported toward the combustion zone and the overall efticiency of the combustion recovery process is increased. injection of a heat absorbing foam into the burn zone of a formation will similarly increase efficiency with less channeling and enhanced conformance.

While particular embodiments of the present invention have been shown and described, it is agparentthat changes and modifications may be made without departing from this invention in its broad W15 and therefore the aim in the appended claims isto cover all such changes and modifications that fallwithinthemie spirit and scope of this invention.

What is claimed is:

I. An injector for downhole rn'st generation including a section of tubing terminated at the lower end by a collar; said injector comprising: admire-shaped inlet section having a plurality of apertures therein for ad mitting fluids; an intermediate section attached to the lower end of said inlet section and sealed to the interior of said collar; and an outlet section including aspray orifice for production of a mist from fluid flowing through said injector.

2. An injector for mist generation including asection of tubing terminated at the lower end by acollar having an internal annular abutment. said injector comprising: a dome-shaped inlet section having a plurality of apertures therein for admitting fluids and a fishing neck mounted to the top; an intermediate section attached to the lower end of said inlet section and sealed to the interior of said collar, said intermediate section including an external annular ridge supported by said abut ment and the seal therebetween including an O-ring; and an outlet section including aspray orifice for production of a mist from fluid flowing through saidinjector and a diverging nozzle to directtbe trajectory of the trust.

3. An injector for downhole mist generation including a section of tubing terminated at the lower end by a collar, said injector comprising: a dome-shaped inlet se tion having a plurality of apertures therein for admitiing fiuids; an intermediate section attached to the lower end of said inlet section and sealed to the interior of said collar; an outlet section including a spray orifice for production of a mist from fluid flowing through said injector; and a central sump aspirator tube in communication with the reduced pressure of the spray orifice and extending from within said injector to the sump of the hole for aspirating and remisting any liquid collected in the sump.

4. An injector for downhole mist generation, comprising: a section of cylindrical tubing; a collar attached to the lower end of the tubing; an intermediate section mounted and axially aligned within said collar and sealed to the interior thereof; an inlet section located within said tubing and attached to the top of said intermediate section, said inlet section including an apertured dome for admitting fluids flowing down said tubing into said intermediate section; and an outlet section attached to the bottom of said intermediate section, said outlet section including a high velocity spray orifice for producing a mist spray and a diverging outlet noale for shaping and directing the mist spray from the nozzle.

5. An injector for downhole mist generation as set forth in claim 4 which also includes: a central sump aspirator tube attached to said inlet section and extending axially through said intermediate section, the high velocity spray orifice, and the outlet nozzle into the sump of the well hole, the interior of said tube being in communication with the low pressure region within the high pressure spray orifice for aspirating and remisting liquid collected in the hole sump. 

1. An injector for downhole mist generation including a section of tubing terminated at the lower end by a collar, said injector comprising: a dome-shaped inlet section having a plurality of apertures therein for admitting fluids; an intermediate section attached to the lower end of said inlet section and sealed to the interior of said collar; and an outlet section including a spray orifice for production of a mist from fluid flowing through said injector.
 2. An injector for mist generation including a section of tubing terminated at the lower end by a collar having an internal annular abutment, said injector comprising: a dome-shaped inlet section having a plurality of apertures therein for admitting fluids and a fishing neck mounted to the top; an intermediate section attached to the lower end of said inlet section and sealed to the interior of said collar, said intermediate section including an external annular ridge supported by said abutment and the seal therebetween including an O-ring; and an outlet section including a spray orifice for production of a mist from fluid flowing through said injector and a diverging nozzle to direct the trajectory of the mist.
 3. An injector for downhole mist generation including a section of tubing terminated at the lower end by a collar, said injector comprising: a dome-shaped inlet section having a plurality of apertures therein for admitting fluids; an intermediate section attached to the lower end of said inlet section and sealed to the interior of said collar; an outlet section including a spray orifice for production of a mist from fluid flowing through said injector; and a central sump aspirator tube in communication with the reduced pressure of the spray orifice and extending from within said injector to the sump of the hole for aspirating and remisting any liquid collected in the sump.
 4. An injector for downhole mist generation, comprising: a section of cylindrical tubing; a collar attached to the lower end of the tubing; an intermediate section mounted and axially aligned within said collar and sealed to the interior thereof; an inlet section located within said tubing and attached to the top of said intermediate section, said inlet section including an apertured dome for admitting fluids flowing down said tubing into said intermediate section; and an outlet section attached to the bottom of said intermediate section, said outlet section including a high velocity spray orifice for producing a mist spray and a diverging outlet nozzle for shaping and directing the mist spray from the nozzle.
 5. An injector for downhole mist generation as set forth in claim 4 which also includes: a central sump aspirator tube attached to said inlet section and extending axially through said intermediate section, the high velocity spray orifice, and the outlet nozzle into the sump of the well hole, the interior of said tube being in communication with the low pressure region within the high pressure spray orifice for aspirating and remisting liquid collected in the hole sump. 